Commonly known in the art are heat exchangers used in connection with an automotive vehicle for cooling the engine of the vehicle. The heat exchanger generally comprises an upper and lower manifold providing fluid reservoirs and a plurality of coolant tubes extending between the manifolds and providing fluid communication therebetween. Coolant passing through the upper and lower manifolds and coolant tubes is maintained at substantially elevated temperatures and pressures under normal operating conditions. A fluid impervious connection must be established between the ends of the coolant tubes and the manifolds to prevent the high pressure coolant from leaking through the interface. Generally, this pressure impervious connection is formed peripherally between end portions of the coolant tubes which are received in corresponding collar openings in each of the manifolds.
For example, the U.S. Pat. No. 4,744,505 to Calleson, issued May 17, 1988, discloses a method for connecting the end portion of a coolant tube to the header wall of a heat exchanger. Calleson generally discloses expanding the end portion of the coolant tube into the collar opening in the header wall to create a tight fit therebetween. However, the Calleson teaching is deficient in that the expansion process is incomplete leaving an annular opening between the collar opening and an unexpanded remaining portion of the tube. This opening must be filled to complete the seal with extensive amounts of solder, weld or the like, to create a fluid impervious and high pressure resistant seal between the tube and collar. The additional step required to fill the opening is time consuming and de to the large annular opening filled between the collar and tube the filler material has a tendency to break loose over time thus permitting leakage.
The U.S. Pat. No. 4,546,824 to Melnyk, issued Oct. 15, 1985, and assigned to the assignee of the subject invention discloses a similar coolant tube to header connection. Each of the tubes include a circular end portion received in a respective collar openings of the header. Each tube end portion is expanded to engage the collar opening and form a fluid impervious seal therebetween. The tubes shown in the Melnyk disclosure are of typical construction in that a seam of overlapping and interlocking material extends the length of each tube. Although the seamed tubing is an economical and efficient method of producing such tubing in large quantities, the thickness of the seam creates problems when the end portion of the tube is expanded to create a peripheral seal with the collar opening. Particularly, a conically tapered flaring tool is used to expand the tube end portion. Because the flaring tool has a circular cross section along its length, the thick seam prevents the wall portions of the tube immediately adjacent the seam from being properly expanded into the collar opening to perfect an adequate seal. As a result of the incomplete seal, the openings left between the collar opening and the tube adjacent the seam, likewise must be filled with extensive amounts of solder, or other similar filling material and as stated previously, the extensive filling material filling the opening has a tendency to break loose over time and result in leakage.
The U.S. Pat. No. 4,455,917 to Michael et al, issued Jul. 17, 1984 discloses a typical prior art flaring tool for expanding the end portion of the coolant tube against the collar opening of the header in a heat exchanger.